A long-term goal of this research has been to assess the role of adenosine 3',5'-phosphate (cyclic AMP) in the neurohumoral regulation of central nervous system (CNS) function. The principal emphasis has been the regulation of cyclic AMP metabolism in CNS tissue. Currently the project is aimed at elucidating mechanisms underlying potentiative interactions and at identifying endogenous humoral agents capable of influencing the accumulation of cyclic AMP. Specifically, it is proposed to: 1) investigate the role of Ca ions in the effects of 40 mM KCl on cyclic AMP levels in guinea pig brain slices by comparing broken-cell preparations from cerebral cortex and cerebellum with regard to the impact of EGTA and Ca ions on the activities of adenylate cyclase and phosphodiesterase; 2) investigate the role of Ca ions in the potentiative interactions between pairs of agonists in brain slices from various species of adult, fetal and neonatal animals by evaluating the impact on cyclic AMP accumulation of deletion of Ca ions, addition of extra Mg ions and addition of colchicine of vinca alkaloids upon responses to norepinephrine, histamine, adenosine and glutamate, singly and in combinations; 3) search for potentiative interactions between pairs of agonists in dispersed-cell and cultured cell preparations derived from cerebral tissue of fetal guinea pigs and of perinatal rabbits; 4) develop a semi-quantitative immunohistochemical procedure for the localization of cyclic AMP by exposing thin frozen sections to UV light and by use of a complex between an antibody and a radioactive ligand; and 5) search for unidentified endogenous substances capable of stimulating the accumulation of cyclic AMP by devising suitable assay conditions and by evaluating the potential actions of substances known to be present in brain extracts.